CVE-2026-87929Public exploitNetwork attack vector

Administrator takeover via forged session cookie

Published Sep 9, 2026 · Updated Sep 9, 2026

Authentication bypass in MaxSite CMS 0.78 through 109.6 allows remote attackers to gain administrator access via a forged session cookie. The default application/config/config.php key signs plaintext ci_session data with HMAC-SHA1, while failed credential decryption is compared as zero during database revalidation. No credentials or user interaction are required; a crafted Cookie header reaches the administrator panel and grants control of site content, users, settings, and templates.

CVSS severity9.8
Critical
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in MaxSite CMS 0.78 through 109.6 allows remote attackers to gain administrator access via a forged session cookie. The default application/config/config.php key signs plaintext ci_session data with HMAC-SHA1, while failed credential decryption is compared as zero during database revalidation. No credentials or user interaction are required; a crafted Cookie header reaches the administrator panel and grants control of site content, users, settings, and templates.

The record

CVE
CVE-2026-87929
Published
Sep 9, 2026
Updated
Sep 9, 2026
Vendor
MaxSite
Product
MaxSite CMS
Classifications
CWE-321, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 9, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.78 <=109.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

MaxSite · MaxSite CMSversion=0.78 <=109.6

Published CVSS scores

9.8VulnCheckCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.3VulnCheckCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-321Use of Hard-coded Cryptographic Key
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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